\(=2^{n+3-n}-5\cdot2^{n+2-n}+2^{n+1-n}\\ =2^3-5\cdot2^2+2^1=8-20+2=-10\)
\(\left(2^{n+3}-5\cdot2^{n+2}+2^{n+1}\right):2^n\)
\(=2^n\cdot8:2^n-5\cdot2^n\cdot4:2^n+2^n\cdot2:2^n\)
\(=8-5\cdot4+2\)
=-10
\(=2^{n+3-n}-5\cdot2^{n+2-n}+2^{n+1-n}\\ =2^3-5\cdot2^2+2^1=8-20+2=-10\)
\(\left(2^{n+3}-5\cdot2^{n+2}+2^{n+1}\right):2^n\)
\(=2^n\cdot8:2^n-5\cdot2^n\cdot4:2^n+2^n\cdot2:2^n\)
\(=8-5\cdot4+2\)
=-10
cho: (x-1)^3+(y-2)^3 -(Z-#)^3=0
tính : (x-1)^2n-1 +(y-z)^2n+1 +(z-3)^2n+1
tính :
(2x^2n + 3x^2n-1). ( x^1-2n - 3x^2-2n)
Cho:
\(A=\dfrac{1}{1.\left(2n-1\right)}+\dfrac{1}{3.\left(2n-3\right)}+...+\dfrac{1}{\left(2n-3\right).3}+\dfrac{1}{\left(2n-1\right).1}\) \(B=1+\dfrac{1}{3}+...+\dfrac{1}{2n-1}\) (với n ∈ N*).
Tính \(\dfrac{A}{B}\)
1) Tìm x biết: 5(x^2-1)+x(1-5x)= x-2
2) Chứng minh các đẳng thức sau:
a) (x+y+z)^3 = x^3+y^3+z^3+3(x+y)(y+z)(z+x)
b) x^2n+1 +y^2n+1 = (x+y)(x^2n-x^2n-1 y+x^2n-2 y^2- ...+x^2 y^2n-2 -xy^2n-1 +y^2n)
Làm tính nhẫm: (2x2n+3x2n-1)(x1-2n- 3x2n-2)
(2.x2n+3.x2n-1)(x1-2n-3.x2-2n)
Cho 3 số t/m x + y + z = 6 và \((x-1)^3 +(y-2)^3 +(z-3)^3 =0\)
Tính T = \((x-1)^{2n+1} + (y-2)^{2n+1} + (z-3)^{2n+1} \)
cho A=1/1*(2N-1)+1/3*(2n-3)+...+1/(2n-1)*1
B=1+1/3+1/4=...+1/n
tính A:B
Bài 1: Thực hiện phép tính:
A = \(\left(2x^{2n}+3x^{2n-1}\right)\left(x^{1-2n}-3x^{2-2n}\right)\)
B = \(\left(3x^{2m-1}-\frac{3}{7}y^{3n-5}+x^{2m}y^{3n}-3y^2\right).8x^{3-2m}y^{6-3n}\)